The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the electronics industry utilized various approaches to forming voltage references for audio amplifiers. These audio amplifiers required a stable reference voltage with low settling times in order to provide high quality audio amplification that had good power supply noise rejection. In general, a very high quality voltage regulator was utilized to provide a power source and the reference voltage was developed from this power source. Often, a filter was used on the output of the voltage reference in order to improve power supply noise rejection at low frequencies, such as frequencies below about five Hz. One problem with such audio amplifier systems was system cost. The low dropout voltage regulator was complicated and expensive to implement and increased system cost. Additionally, the filter often had a cut-off frequency of approximately two to three Hz. Such high cut off frequencies resulted in poor power supply noise rejection.
Accordingly, it is desirable to have an audio amplifier voltage reference that has a low cut-off frequency, that does not require a high quality voltage regulator, and that has a fast settling time.